FIG. 1 is a cross-sectional view of a fuel pump. As described in FIG. 1, when starting engine of a vehicle, generally its fuel pump supplies power to an armature 10 through a carbon brush 100 and a commutator 300. As the armature 10 of the fuel pump is driven, an impeller connected to the armature 10 rotates to discharge fuel from a fuel tank, and thereby the fuel discharged through the fuel pump is supplied to the engine in constant pressure.
At this moment, the carbon brush 100 and the commutator 300 are contacted to each other, so that the carbon brush 100 moves in a rotational direction of the commutator 300. However since the carbon brush 100 adhered to an inside wall of a brush holder 400 contacts the rotating commutator 300, if the carbon brush 100 is shaken, the carbon brush 100 and the commutator 300 may be temporarily detached. Then, rotational force of fuel pump and discharge performance may be reduced, and the engine may be stopped during driving.
According to JP 5261486 (“Electric pump device”, May 2, 2013, hereinafter referred to as prior art), to prevent shake of brush, an inside wall of a brush holder is inclined for a brush to be more easily adhered to the inside wall whenever a commutator rotates. However, the prior art does not disclose a fundamental method to prevent shake of brush.